1. Field of the Invention
The present invention relates to a technology for inspecting the appearance of an inspection piece and, more particularly, to a technology for inspecting the appearance of a package board by using multiple imaging units.
2. Description of the Related Art
Recently, electronic boards are used in a vast majority of equipment. Miniaturization, slim size and low price are persistent goals to be achieved in equipment in which electronic boards are used. For this purposes, high-integration design is practiced. Elements essential to achieve high-integration design include high-density packaging technology as well as availability of various design tools and advancement in semiconductor technology. Fabrication technology and inspection technology are important considerations to achieve high-density packaging. There is proposed a technology of using image recognition technology to inspect a printed board (hereinafter, referred to as a “board”) on which components are already mounted.
For example, patent document No. 1 proposes a soldering method for a double-sided board, wherein soldering condition is monitored using images of both surfaces of a board obtained by irradiating the board with X-ray. As an another example, patent document No. 2 proposes an inspection method for a double-sided board in which a back image data is derived from a difference between front image data showing components mounted only on the front surface of the board and double-face image data showing components mounted on both surfaces of the board, and in which a determination is as to whether components are properly mounted on the front surface, by referring to a difference between the double-face image data of the board actually inspected and the back image data.
[patent document No. 1]: JP 2001-50730 A
[patent document No. 2]: JP 2002-158500 A
While technologies have been proposed for determining whether components are properly mounted on a board by referring to the images of both surfaces of the board, no technology has been proposed for efficiently imaging and analyzing both surfaces of a board on which components are mounted. With the current status of technology, an extended period of time is required if inspection depends on the recognition of a high-definition image. Further reduction in inspection time is desired.